In farming, an incentive exists to improve harvest efficiency. The overall effectiveness of agricultural harvest machinery is dependent upon a combination of its design, reliability, and operating conditions. The primary functional objective of harvesting equipment such as combines is to collect the crop in the minimum amount of time with the least losses and product damage and the lowest capital and operating costs. However, the combine encounters a wide range of harvesting situations and crops. Because of these factors and the potential return obtainable for performance improvements, development of a more effective drive system for the grain threshing mechanism of the combine is desirable.
One known development in grain threshing systems is the rotating concave threshing mechanism which utilizes a rotor assembly positioned within a rotating concave assembly, each driven independently and rotatable in a selected direction one relative to the other. This improved mechanism has increased the productivity and efficiency of threshing grains, but, owing to its construction, is susceptible to stalling when encountering physical properties of the material entering the mechanism which tend to overload the system.
Physical properties which can generate stalling of the threshing system when encountered at normal operating speeds of the system, are for example, intermittent high density of the crop, scattered patches of weeds having exceedingly high moisture content, crops which have been broken down by high winds, hail, and rain, and solid articles such as rocks and wood that are delivered to the threshing system when attempting to harvest such "downed" crops.
Previously used methods of preventing stalling or plugging the threshing mechanism are, for example, slowing down the feed rate of material delivered to the threshing mechanism by slowing down the feeder chain, adjusting the forward speed of the combine, and reversing rotational direction of the rotating concave assembly to clear plugs. These methods have been found to be relatively ineffective in maintaining productivity and efficiency.
One characteristic of the rotating concave threshing mechanism is the rotating speeds required for the rotor assembly. Generally, only a few speeds are required and it is known to employ multi-ratio transmissions in rotor assembly drive systems to provide selectability of predetermined rotor assembly speeds. However, for a more productive and efficient operation, it is desirable to have still greater flexibility in speed selection. Some known threshing systems provide an infinitely variable speed capability. Infinitely variable speed drive systems, however, tend to be bulky, complex, have short component life, and are expensive.
Thus, what is needed is a drive system for the rotor assembly of a combine threshing mechanism that provides the capability to selectably drive the rotor assembly within several distinct speed ranges.
The present invention is directed to overcome one or more of the problems as set forth above.